Dose setting assembly with slack reducing feature

Abstract

Add-on device for a drug delivery pen device, comprising a drive member adapted for coupling to a dose dial member of the pen device, a dial member adapted to rotate the drive member in first and second directions to set/adjust a pen dose, a release member axially moveable to actuate a pen device release button, a linear-to-rotational converter mechanism adapted to convert axial movement of the release member to rotational movement of the drive member in a first direction, whereby, when the add-on device is mounted on the drug delivery pen device: the dose dial member of the pen device is biased in the first direction by the drive member thereby taking up rotational slack in the pen device.

1 . An add-on device adapted to be releasably mounted on a drug delivery device, the drug delivery device comprising:
 a housing defining a reference axis,   a drug reservoir or structure for receiving a drug reservoir, and   drug expelling structure comprising:
 a dose setting member adapted to rotate in a first direction to incrementally set a dose, and rotate in an opposed second direction to incrementally reduce a set dose, the dose setting member being arranged at the proximal end of the housing, and 
 a release member actuatable between a proximal position and a distal position, the proximal position allowing a dose amount to be set, the distal position allowing the drug expelling structure to expel a set dose, 
   
       the add-on device comprising:
 an add-on housing adapted to be releasably attached to the drug delivery device housing in an axially and rotationally non-moveable position, 
 a drive member adapted to be mounted rotationally locked on the dose setting member, 
 an add-on dose setting member coupled to the add-on housing rotatable free but axially locked and adapted to rotate in the first direction to set a dose, and rotate in the opposed second direction to reduce a set dose, 
 an actuatable add-on release member axially moveable relative to the add-on dose setting member between:
 (i) a proximal dose setting position in which the add-on dose setting member can be operated to rotate the drive member and thereby, when mounted on the dose setting member, set a dose, and 
 (ii) a distal dose expelling position in which the release member, when the add-on device is mounted on the drug delivery device, is moved to its distal position to release a set dose, 
 
 a linear-to-rotational converter mechanism adapted to convert axial movement of the add-on release member, when the add-on release member is moved from the proximal position towards the distal position, to rotational movement of the drive member in the first direction, 
 
       whereby, when the add-on device is mounted on the drug delivery device:
 the dose setting member is biased in the first direction by the drive member when the add-on release member is moved from the proximal position towards the distal position. 
 
     
     
         2 . The add-on device as in  claim 1 , further comprising:
 a torque limiter preventing, when the add-on device is mounted on the drug delivery device, that a torque above a pre-set level can be transferred to the drive member when the add-on release member is moved from the proximal position towards the distal position.   
     
     
         3 . The add-on device as in  claim 2 , wherein the torque limiter comprises:
 a flexible element adapted to deform when a torque above the pre-set level has been transferred to the drive member, or   is in the form of a ratchet torque limiter.   
     
     
         4 . The add-on device as in  claim 1 , wherein the rotational movement is generated by a cam-follower mechanism. 
     
     
         5 . The add-on device as in  claim 4 , wherein the cam-follower mechanism further comprises a track and a follower arranged in the track, the track having a radial component, the follower and track moving axially relative to each other member when the add-on release member is moved from the proximal position towards the distal position. 
     
     
         6 . The add-on device as in  claim 5 , wherein the follower comprises a flexible arm adapted to bend when a torque above a pre-set level has been transferred to the drive member. 
     
     
         7 . The add-on device as in  claim 1 , the drug expelling structure comprising:
 an indicator adapted to rotate during expelling of a dose amount, the amount of rotation being indicative of the size of the expelled dose amount, and   
       the add-on device comprising:
 sensor structure operatable to detect the amount of rotation of the indicator during expelling of a dose amount, 
 
       wherein:
 rotational movement has been applied to the drive member prior to the sensor structure being operated, 
 
       whereby:
 when the add-on device is mounted on the drug delivery device, it is assured that rotational slack in the drug expelling structure has been removed by rotation of the dose setting member in the first direction. 
 
     
     
         8 . The add-on device as in  claim 7 , further comprising an actuator structure adapted to move axially and engage the release member when the add-on release member is actuated, wherein the sensor structure is coupled to and moves axially with the actuator structure. 
     
     
         9 . The assembly comprising a drug delivery device as defined in  claim 1  and an add-on device as defined in  claim 1 . 
     
     
         10 . The assembly comprising a drug delivery device and add-on device as defined in  claim 7 . 
     
     
         11 . The assembly as in  claim 10 , wherein:
 the indicator comprises a plurality of dipole magnets, and   the sensor comprises:
 a plurality of magnetometers arranged non-rotational relative to the housing in a mounted state and adapted to determine magnetic field values from the plurality of dipole magnets, and 
 processor structure configured to determine on the basis of measured values from the plurality of magnetometers a rotational position and/or a rotational movement of the indicator. 
   
     
     
         12 . The assembly comprising a drug delivery device and add-on device as defined in  claim 1 , wherein:
 the drug expelling structure comprises an indicator adapted to rotate during expelling of a dose amount, the amount of rotation being indicative of the size of the expelled dose amount, and   the drug delivery device is adapted for mounting of a dose logging add-on device comprising sensor structure operatable to detect the amount of rotation of the indicator during expelling of a dose amount.   
     
     
         13 . The assembly comprising a drug delivery device and add-on device as defined in  claim 1 , wherein:
 the drug expelling structure comprises an indicator adapted to rotate during expelling of a dose amount, the amount of rotation being indicative of the size of the expelled dose amount, and   the assembly further comprises a dose logging add-on device adapted to be mounted on the drug delivery device, comprising sensor structure operatable to detect the amount of rotation of the indicator during expelling of a dose amount.   
     
     
         14 . The assembly as in  claim 13 , wherein:
 the indicator comprises a plurality of dipole magnets, and   the sensor structure comprises:
 a plurality of magnetometers arranged non-rotational relative to the housing in a mounted state and adapted to determine magnetic field values from the plurality of dipole magnets, and 
 processor structure configured to determine on the basis of measured values from the plurality of magnetometers a rotational position and/or a rotational movement of the indicator. 
   
     
     
         15 . A unitary drug delivery device, comprising:
 a housing defining a reference axis,   a drug reservoir or structure for receiving a drug reservoir,   drug expelling structure comprising:
 an inner dose setting member adapted to rotate in a first direction to set a dose, and rotate in an opposed second direction to reduce a set dose, 
 an inner release member actuatable between a proximal position and a distal position, the proximal position allowing a dose amount to be set, the distal position allowing the drug expelling structure to expel a set dose, and 
 an indicator adapted to rotate during expelling of a dose amount, the amount of rotation being indicative of the size of the expelled dose amount, 
   a user dose setting member coupled to the housing rotatable free but axially locked and adapted to rotate in the first direction to set a dose, and rotate in the opposed second direction to reduce a set dose,   an actuatable user release member axially moveable relative to the user dose setting member between (i) a proximal dose setting position in which the user dose setting member can be operated to rotate the inner dose setting member to set a dose, and (ii) a distal dose expelling position in which the inner release member is moved to its distal position to release a set dose, and   a linear-to-rotational converter mechanism adapted to convert axial movement of the user release member, when the user release member is moved from the proximal position towards the distal position, to rotational movement of the inner dose setting member in the first direction.